Originally Posted by Thelis
RAID stands for: Redundant Arrays of Inexpensive (Independent has replaced Inexpensive) Disks.
It basically means that multiple HDDs will work as one, and thus achieving better performance than if you get 1 large HDD. So no, if they are in RAID, they work together.
Master/slave though is different.
This would also depend on the RAID configuration he is using. Your talking about a striped array, but he is talking about a mirrored array, so it depends on the setup he is getting mate.
These are the different types, you can also combine these aswell
RAID 0: Striped Set (2 disks minimum) without parity. Provides improved performance and additional storage but no fault tolerance from disk errors or disk failure. Any disk failure destroys the array, which becomes more likely with more disks in the array. The reason a single disk failure destroys the entire array is because when data is written to a RAID 0 drive, the data is broken into "fragments". The number of fragments is dictated by the number of disks in the drive. Each of these fragments are written to their respective disks simultaneously on the same sector. This allows smaller sections of the entire chunk of data to be read off the drive in parallel, giving this type of arrangement huge bandwidth. When one sector on one of the disks fails, however, the corresponding sector on every other disk is rendered useless because part of the data is now corrupted. RAID 0 does not implement error checking so any error is unrecoverable. More disks in the drive means higher bandwidth, but greater risk of data loss.
RAID 1: Mirrored Set (2 disks minimum) without parity. Provides fault tolerance from disk errors and single disk failure. Increased read performance occurs when using a multi-threaded operating system that supports split seeks, very small performance reduction when writing. Array continues to operate so long as at least one drive is functioning.
RAID 3 and RAID 4: Striped Set (3 disk minimum) with Dedicated Parity, the parity bits represent a memory location each, they have a value of 0 or 1, whether the given memory location they represent, is empty or full, thus enhancing the speed of read and write. This mechanism provides an improved performance and fault tolerance similar to RAID 5, but with a dedicated parity disk rather than rotated parity stripes. The single disk is a bottle-neck for writing since every write requires updating the parity data. One minor benefit is the dedicated parity disk allows the parity drive to fail and operation will continue without parity or performance penalty.
RAID 5: Striped Set (3 disk minimum) with Distributed Parity. Distributed parity requires all but one drive to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure. Upon drive failure, any subsequent reads can be calculated from the distributed parity such that the drive failure is masked from the end user. The array will have data loss in the event of a second drive failure and is vulnerable until the data that was on the failed drive is rebuilt onto a replacement drive.
RAID 6: Striped Set (4 disk minimum) with Dual Distributed Parity. Provides fault tolerance from two drive failures; array continues to operate with up to two failed drives. This makes larger RAID groups more practical. This is becoming a popular choice for SATA drives as they approach 1 Terabyte in size. This is because the single parity RAID levels are vulnerable to data loss until the failed drive is rebuilt. The larger the drive, the longer the rebuild will take. With dual parity, it gives the array time to rebuild onto a large drive with the ability to sustain another drive failure.
Even more info here http://en.wikipedia.org/wiki/RAID